Ink jet recording apparatus

ABSTRACT

An ink jet recording apparatus comprises a counter or timer for timing the period during which printing does not take place even though a printing control device is supplied with electric power; a flip-flop circuit actuated by a set signal delivered from said counter upon completion of its counting cycle; an AND gate supplied with an output from said flip-flop circuit when it is set and being further supplied with printing instruction signals; and a pump driving circuit supplied with an output from said AND gate through a differentiation circuit so as to drive said pump for preliminary ejection of ink through a nozzle for a short time, thereby quickly effecting preliminary ejection of ink upon receipt of the printing instructions. The preliminary ejection is only carried out when printing has not taken place during a period of time corresponding to the timing period of the counter or timer.

United States Patent Kashio Dec. 9, 1975 INK JET RECORDING APPARATUS 75 memo: T hi K Y t J Primary Examiner-Joseph W. Hartany J r 08 as '0 Oma 0 apan Attorney, Agent, or Firm Flynn & Frishauf [73] Assignee: Casio Computer Co., Ltd., Yomato,

Japan 57 ABSTRACT [22] Filed July 8, 1974 An ink 'et recordin a aratus com rises a counter or J g PP P [21] Appl NO 486 480 timer for timing the period during which printing does not take place even though a printing control device is Related U.S. Application Data supplied with electric power; a flip-flop circuit actu- [63] COminum-mn f NO 314999. Use 14, 1972 ated by a set signal delivered from said counter upon abandoned. completion of its counting cycle; an AND gate sup plied with an output from said flip-flop circuit when it Foreign Application Priority Data is set and being further supplied with printing instruc- Dec. 16, 197i Japan u 46-l0l443 signals; and 3 Pump driving Circuit Supplied an output from said AND gate through a difierenti- 52 C| U 346/; 346/ ation circuit so as to drive said pump for preliminary [51] IL z v I V G011) 15/18 ejection of ink through a nozzle for a short time 58 Field of Search 346/75, 140 thereby quickly effecting Preliminary election of ink upon receipt of the printing instructions. The prelimi- [56} References cu nary ejection is only carried out when printing has not UNITED STATES PATENTS taken place during a period of time corresponding to the timing period of the counter or timer. 3.l36 S94 6/l964 Ascoli .l 346/75 I 3,488 664 W970 Winston 346/75 Clalms. 2 Drawing g r s ELECTRIC SOURCE 42- MAIN E CONTROL DEVICE EEL/AY I CIRCUIT S R l6 TIMER L Fl UNIT F oEFLEchoN ClRCUlT .9 l

OIFFERENTIATIOF 20 ClRCUlT lNK lNK i RECORDlNG TAM: PUMP UNIT U.S. Patent Dec. 9, 1975 Sheet 1 of2 3,925,789 I ELECTRIC SOURCE MAIN CONTROL DEVICE I *0ELAY CIRCUlT 3 R 16 TIMER F/ 5 F DEFLECTION C\RCU1T 19 DIFFERENTIATION 2 CIRCUIT INK RECORDING TANK PUMP UMT INK JET RECORDING APPARATUS BACKGROUND OF THE INVENTION This is a continuation of application Ser. No. 314,999, filed Dec. l4, 1972, now abandoned.

This invention relates to an improved ink jet recording apparatus which ejects ink in fine particles and controls the scattering direction of ink particles by means of a deflection system, thereby enabling characters, l

patterns, etc. to be distinctly presented on a sheet of recording paper.

An ink jet recording apparatus generally consists in ejecting ink in fine particles from a nozzle communicating with an ink tank utilizing a strong electric field, and scanning scattering ink particles by a deflection system including deflection plates in accordance with character signals conducted to said deflection system, thereby drawing characters, patterns, etc. on a sheet of recording paper. The ink jet nozzle has an extremely small inner diameter, such as about 0.1mm. In a rest condi tion, therefore, where there is not ejected any fresh ink, it some times happens that the ink already remaining in the ink nozzle tip is considerably retracted or solidified upon exposure to the open air. For example, if, after printing is stopped for a certain length of time, the recording apparatus is started, the initial line wili fail to present distinct characters, patterns, etc., because fresh ink can not be ejected smoothly.

To avoid such drawbacks, there may be contemplated, for example, the process of actuating the ink jet system for l to 3 seconds when the recording apparatus is supplied with power for start, but before there is supplied a printing instructing signal, pushing fresh ink up to the opening of the ink jet nozzle so as to eliminate the lumpy ink previously solidified therein. Namely, this process consists in generating a signal instructing the ejection of ink l to 3 seconds at the same time the recording apparatus is supplied with power and effecting the ejection of good fresh ink upon receipt of the succeeding signal instructing said ejection, thereby printing distinct characters, patterns, etc.

However, where there is used a printing apparatus thus arranged as an output means for an electronic computer or telecommunication apparatus, the apparatus will often have to be kept in a state waiting for printing after power supply. Accordingly, even when the preliminary ejection of ink is carried out at the time of power supply to attain the normal operation of the ink jet nozzle, the ink will considerably retreat from the nozzle tip or be hardened, if the aforesaid waiting state continues long, probably failing to effect good printing.

It is accordingly the object of this invention to provide an ink jet recording apparatus permitting the smooth ejection of ink upon receipt of printing instructions even when the apparatus is kept long in a waiting state for printing after power supply, thereby attaining the distinct printing of characters, patterns, etc.

SUMMARY OF THE INVENTION According to one aspect of this invention, there is provided an ink jet recording apparatus comprising a printing control device; means for detecting printing instructions given to said printing control device; and means for preliminarily ejecting ink for a short time from the nozzle to an ink collector upon receipt of an output from the printing instructions detecting means.

According to another aspect of this invention, there is provided an ink jet recording apparatus comprising a printing control device; means for detecting printing instructions given to said printing control device; a timer for counting the length of a nonprinting period while the printing control device is supplied with power; means for detecting whether the nonprinting period previously counted by said timer has exceeded a predetermined time and memorizing said excess; means for detecting printing instructions given to the printing control device when the memory means is operated; and means for preliminarily ejecting ink for a short time from the nozzle to an ink collector upon receipt of an output from the printing instructions detecting means.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block circuit diagram of an ink jet record ing apparatus according to an embodiment of this invention; and

FIG. 2 is a block circuit diagram of an ink jet record ing apparatus according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral ll represents a main control device for undertaking the control of printing. This control device 11 is put into operation when a power source switch 12 is thrown to the on position. Upon receipt of printing instructions, the main control device 1] drives an ink pump 13, which may be a conventional ink pump, causing ink to be conducted under pressure from an ink tank 14, which may be a conventional ink tank, to the ink jet nozzle of a recording section 15, and be ejected from the nozzle in fine particles. The deflection circuit 16 is coupled to the main control device 1 and is actuated by signals of characters being printed. This deflection circuit 16 deflects ink particles ejected from the nozzle to be directed to a sheet of recording paper, thereby printing characters of patterns. The ink pump 13, ink tank 14, recording section 15 and deflection circuit 16 are conventional types of devices which are interconnected in a conventional manner.

Power is also supplied through the power supply switch 12 to a conventional timer 17 for its operation. Upon the lapse of a preset period of time, the timer 1'! is so set as to generate an output signal to set a conv entional flip-flop circuit 18, thereby obtaining an output signal from said circuit 18. An output from the flip-flop circuit 18 is supplied to an AND gate 19 together with a printing instructing signal from the main control device 11. An output from the AND circ uit 19 is supplied to the ink pump 13 for its drive in the form of pulses through a conventional differentiation circuit 20, if required. An output from the AND circuit 19 is also conducted to the deflection circuit 16, causing ejected ink particles to be deflected to an ink collector disposed outside of the recording paper. The timer 17 is reset by a printing instructing signal delivered from the main control device 11, and the flip-flop circuit 18 is reset by a signal obtained by passing the printing instructing signal through a conventional delay circuit 21.

When the power supply switch I2 is thrown on, the recording apparatus of this invention is brought to a state ready for printing. At the time of power supply, a power supply detecting signal, if necessary, actuates the ink pump 13 and deflection circuit 16, causing ink to be ejected for a short time to an ink collector, which, upon receipt of printing instructions, is brought to a state ready for printing. Where, under this condition, the printing instructions are supplied to the main control device 11, the ink pump 13 is driven to eject ink from the nozzle, causing characters or patterns to be printed on the recording paper according to the printing instructions by the action of the deflection circuit 16. The timer 17 which is also actuated at the time of power supply is reset each time the main printing control device 11 is supplied with fresh printing instructions. For example, where the timer 17 is set at 30 min utes, it does not generate any output signal, if there are given printing instructions during said 30-minute period, thereby preventing ink from being preliminarily ejected from the nozzle by an output signal from the timer 17. Upon the lapse of 30 minutes after there are given printing instructions, the timer 17 generates an output signal to set the flip-flop circuit 18. Where, under this condition, the main printing control device 11 is supplied with printing instructions, the AND gate 19 produces an output signal which is conducted to the differentiation circuit 20. As a result, said differentiation circuit 20 provides, for an extremely short period of time, instructions to drive the ink pump 13. Thus, ink is preliminarily ejected from the nozzle for a very short time of, for example, 0.1 second, enabling normal printing to be carried out by the recording section substantially at the start. In this case, an output from the AND gate 19 is also supplied to the deflection circuit 16, causing ink particles ejected from the nozzle to be directed to the recording paper. The above-mentioned preliminary ejection of ink from the nozzle of the recording section 15 has only to be effected only for a sufficient time to print several characters. If said preliminary ejection is so effected upon receipt of printing instructions as to prevent normal printing during that time. then the printing of characters will not be affected. Particularly, the recording apparatus of this invention is designed to store an input signal for printing temporarily in a buffer register and generate character signals by reading out the input signals thus stored. If, therefore, preliminary ejection of ink is undertaken while the printing input signal is still stored in the buffer register, then there will be attained normal printing immediately after said preliminary ejection. An output subsequently delivered from the main printing control device 11 resets the timer and an output from the delay circuit 21 resets the flip-flop circuit 18, bringing the recording apparatus back to its original position.

Depending on the condition in which the delay circuit 2] is set, the duration in which the ink pump 13 is supplied with a drive signal can be controlled according to the time the flip-flop circuit 18 is reset. In such case the differentiation circuit may be omitted.

Where, with the recording apparatus of the aforesaid arrangement, the nonprinting period after the turning on of the power supply exceeds the time at which the timer 17 was previously set, ink is first preliminarily ejected upon receipt of the printing instructions and normal printing is commenced by character signals only after the nozzle is brought to a state adapted for normal ejection of ink, thus always enabling characters or patterns to be distinctly presented from the very outset. The timer 17 is set at such a maximum time as al lows the nozzle to keep a normal condition without car- 4 rying out preliminary ejection of ink. Said maximum time roughly ranges between 15 to 30 minutes.

FIG. 2 omits a power supply circuit. However, the following description is given on the assumption that the power supply source is always actuated. Reference numeral 41 denotes a buffer register for storing a printing output. This buffer register 41 stores signals representing characters being recorded. The character sig nals stored in the buffer register 41 are read out by synchronizing pulses delivered from a source 22, and shifted to a character signal generating register 23. An output from the character signal generating register 23 is supplied to a character signal generator 24. Character signals produced by said generator 24 are conducted to a circuit 25 for controlling a character composing counter 26. An output from the control circuit 25 controls the counting of the character composing counter 26. As a result, the character composing counter 26 generates a digital output acting as a deflection signal for determining the extent to which the de flection system deflects ink particles in the X and Y di rections.

For example, where characters are formed of a series of dots, character signals from the character generator 24 are read out by synchronizing pulses from the source 22. The positions of the individual dots constituting characters being printed are indicated in the form of digital values in the X and Y directions. These digital values are converted into analog signals by digital-to-analog converters 27 and 28, and supplied to deflection circuits 29 and 30 acting in the X and Y directions respectively to control the deflection voltage impressed on the deflection plates 31 and 32 of the recording section 15 similarly acting in the X and Y directions respectively.

The character signal generating register 23 produces character signals and supplies said signals to the printing control circuit 33. An output from said control circuit 33 controls a circuit 34 for driving the ink pump 13. The drive of the pump 13 causes ink to be supplied under pressure to the nozzle 35 of the recording section 15. Further, there is impressed a high DC. voltage across the nozzle and an acceleration electrode 37 by a high pressure (impressing) circuit 36 so as to eject ink particles from the nozzle 35 to a platen 38 on which the recording paper is supported. The printing control circuit 33 also supplies printing controlling instructions to the circuit 25 for controlling the character composing counter 26. Said counter controlling circuit 25 drives an ink collector specifying circuit 39 while there are not given the printing controlling instructions, and instructs the Y direction deflection circuit 30 to control its Y direction deflection so as to conduct ink particles ejected from the nozzle 35 to an ink collector 40 disposed below the platen 38. The character signal generating register 23 supplies character signals to the character composing counter 26. Where there are not generated character signals, said character composing counter 26 acts as a ring counter. The flip-flop circuit 18 is actuated when there is reached the count at which said counter is set in advance. The flip-flop circuit 18 is of the flip-flop circuit 18.

Character signals stored in the printing output buffer register 41 of the recording apparatus shown in FIG. 2 are read out to the character signal generating register 23 by synchronizing signals from the source 22, and then conducted to the character signal generator 24 which in turn generates character signals. An output from the character signal generator 24 controls the operation of the character composing counter 26 and its control circuit 25. An amount of deflection required to draw characters is indicated in digital signals which are supplied to the digital-to'analog converting circuits 27 and 28. Namely, the recording apparatus of this invention indicates characters, patterns, etc. in the form of a series of dots. Signals of characters or patterns stored in the character signal generating register 23 are converted by the character signal generator 24 into a series of co-ordinate signals representing dots. Said co-ordinate signals are successively read out by the control circuit 25 of the character composing counter 26. Thus the positions of said co-ordinate signals are counted in the X and Y directions of the character composing counter 26. The digital-to-analog converting circuits 27 and 28 produce analog signals corresponding to the positions of dots being printed in the X and Y directions. The analog signals thus produced actuate the X direction deflection circuit 29 and the Y direction deflection circuit 30. These deflection circuits 29 and 30 supply the X direction deflection plate 31 and Y direction deflection plate 32 with deflection voltage corresponding to the positions of dots constituting characters, or patterns. Said deflection plates 31 and 32 properly deflect ink particles ejected from the nozzle 35 by the action of the pump driving circuit 34 actuated by instructions from the printing control circuit 33, thereby enabling characters or patterns to be distinctly drawn on the recording paper supported on the platen 38.

In the nonprinting condition where the printing out put buffer register 41 does not have any character signals stored therein, the character signal generating register 23 also has no character signals stored therein. Accordingly, the character signal generator 24 produces no character signal. Since, under this condition, the printing control circuit 33 generates no signal, the control circuit 25 of the character composing circuit 26 delivers control instructions to the ink collector specifying circuit 39. Where the character signal generating register 23 does not produce any character signal, the character composing counter 26 in the X and Y directions acts as a series of ring counters. Accordingly, the Y direction deflection circuit 30 impresses the Y direction deflection plate 32 with deflection voltage to di rect ink particles ejected from the nozzle 35 toward the ink collector 40. At this time, the character composing counter 26 now acting as a ring counter advances counts upon arrival of a synchronizing signal. When there is completed a cycle of counting, the flip-flop circuit 18 is supplied with a set signal. Where, under this condition, the character signal generating register 23 receives an input character signal, said register 23 supplies for a short time drive instructions to the pump driving circuit 34 through the differentiation circuit 20. Accordingly, ink is preliminarily ejected for a short time from the nozzle 35 to the ink collector 40, bringing the recording apparatus to a state ready for normal printing based on character signals.

While there is made no printing, the character composing countcr 26 acts as a sort of timer. Where the printing time exceeds one cycle of counting made by the ring counter constituted by the character composing counter 26, for example, a period of l5 to 30 minutes, then ink is preliminarily ejected for a very short time from the nozzle 35 to the 'ink collector 40 positioned outside of the recording paper just before the succeeding cycle of normal printing is commenced.

Both embodiments described above are provided with a timer for counting a nonprintin g period while the control device is supplied with power. Where the nonprinting period counted by the timer 17 exceeds the preset time and printing instructions arrive, then ink is preliminarily ejected. Since, however, the amount of preliminarily ejected ink is extremely small, it is possible to eliminate the timer, only provide the printing instructions detecting means and carry out preliminary ejection of ink, each time said printing instructions are received. Still, this process attains good results. It will be noted that said process is covered by this invention. As described above, the ink jet recording apparatus of this invention is characterized in that where the apparatus is supplied with power ready for printing, the arrival of printing instructions is detected; and further where there are detected said printing instructions as well as the moment when the nonprinting period exceeds the preset time, then ink is preliminarily ejected from the nozzle just before the succeeding cycle of normal printing is commenced. This process carries out normal printing after eliminating the undesirable condition in which ink is retracted from the opening of the nozzle or is solidified there, most disturbing the characters or patterns being printed, thereby enabling the characters or patterns to be distinctly drawn from the very outset Accordingly, the recording apparatus of this invention can be effectively used as an output means for computers and telecommunication devices.

What is claimed is:

1. An ink jet recording apparatus comprising:

a recording unit including a nozzle for continuously ejecting ink droplets during a normal printing or recording operation;

means for deflecting said normally ejected ink droplets so as to print characters on a recording medium;

an ink collector for collecting ejected ink droplets which are not used to print characters;

a source of print command signals for instructing the carrying out of a printing operation;

detecting means having an instruction input coupled to said source of print command signals and generating a detection signal responsive to a print command signal, said detecting means including delay means coupled to said recording unit for delaying carrying out of said printing operation for a predetermined period of time; and

preliminary ejection means coupled to said detecting means and to said recording unit, and including means for producing a first nozzle-clearing preliminary ejection of ink from said nozzle for a first given period of time during said predetermined period of time responsive to said detection signal from said detecting means, and means for then producing a second preliminary ejection of ink for a second given period of time during said predeter mined period of time in order to produce a steady ink flow from the nozzle, said first given period of time being much longer than said second given period of time;

7 said deflection means being responsive to outputs of said detecting means and said preliminary ejection means for deflecting said preliminarily ejected ink droplets to said ink collector during said predetermined period of time;

said printing operation being carried out after the expiration of said predetermined period of time 2. Apparatus according to claim 1 wherein said pre liminary ejecting means includes means responsive to application of electrical power to said recording apparatus so as to produce said first preliminary ejection of ink when electrical power is applied to said recording apparatus.

3. Apparatus according to claim 1 wherein said preliminary ejection means comprises a differentiation circuit coupled to said recording unit for generating a signal of predetermined duration for causing said preliminarily ejected ink droplets to be ejected for said first given period of time which is a function of the duration of the signal generated by said differentiation circuit.

4. Apparatus according to claim 3 further comprising a timing means coupled to said detecting means for measuring the period of time between print command signals as detected by said detecting means; and control means coupled to and actuated by said timing means and coupled to and controlling said preliminary ejection means so as to produce said first nozzle-clearing preliminary ejection of ink only when the interval between successive print command signals exceeds a predetermined period of time as measured by said timing means and only when said detecting means detects a print command signal which indicates the beginning of a printing instruction.

5. Apparatus according to claim 4 wherein said preliminary ejection means comprises a differentiation circuit coupled to said recording unit for generating a signal of predetermined duration for causing said preliminarily ejected ink droplets to be ejected for said first given period of time which is a function of the duration of the signal generated by said differentiation circuit.

6. Apparatus according to claim 4 wherein said detection means includes means for resetting said timing means upon detection of each print command signal.

7. Apparatus according to claim 4 wherein said control means includes a further delay means for disabling said preliminary ejection means a predetermined period of time after detection of said print command signal.

8. Apparatus according to claim 4 wherein said control means includes memory means for memorizing when the interval between successive print command signals exceeds said predetermined period of time as measured by said timing means.

9. Apparatus according to claim 8 wherein said delay means is coupled to said memory means for resetting said memory means after said predetermined period of time.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENTNO. 3,925,789

DATED December 9, i975 INVENTOR(S) Toshio Kashio It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the initial page of the patent, change the address of the Assignee from "Yomato, Japan" to --Tokyo, Japa Signed and Scaled this twentieth Day of April1976 [SEAL] I Arrest:

RUTH C. MASON C. MARSHALL DANN :illvsling 01TH?! ('mnmissr'nm-r uflan'nls and Trademarks 

1. An ink jet recording apparatus comprising: a recording unit including a nozzle for continuously ejecting ink droplets during a normal printing or recording operation; means for deflecting said normally ejected ink droplets so as to print characters on a recording medium; an ink collector for collecting ejected ink droplets which are not used to print characters; a source of print command signals for instructing the carrying out of a printing operation; detecting means having an instruction input coupled to said source of print command signals and generating a detection signal responsive to a print command signal, said detecting means including delay means coupled to said recording unit for delaying carrying out of said printing operation for a predetermined period of time; and preliminary ejection means coupled to said detecting means and to said recording unit, and including means for producing a first nozzle-clearing preliminary ejection of ink from said nozzle for a first given period of time during said predetermined period of time responsive to said detection signal from said detecting means, and means for then producing a second preliminary ejection of ink for a second given period of time during said predetermined period of time in order to produce a steady ink flow from the nozzle, said first given period of time being much longer than said second given period of time; said deflection means being responsive to outputs of said detecting means and said preliminary ejection means for deflecting said preliminarily ejected ink droplets to said ink collector during said predetermined period of time; said printing operation being carried out after the expiration of said predetermined period of time.
 2. Apparatus according to claim 1 wherein said preliminary ejecting means includes means responsive to application of electrical power to said recording apparatus so as to produce said first preliminary ejection of ink when electrical power is applied to said recording apparatus.
 3. Apparatus according to claim 1 wherein said preliminary ejection means comprises a differentiation circuit coupled to said recording unit for generating a signal of predetermined duration for causing said preliminarily ejected ink droplets to be ejected for said first given period of time which is a function of the duration of the signal generated by said differentiation circuit.
 4. Apparatus according to claim 3 further comprising a timing means coupled to said detecting means for measuring the period of time between print command signals as detected by said detecting means; and control means coupled to and actuated by said timing means and coupled to and controlling said preliminary ejection means so as to produce said first nozzle-clearing preliminary ejection of ink only when tHe interval between successive print command signals exceeds a predetermined period of time as measured by said timing means and only when said detecting means detects a print command signal which indicates the beginning of a printing instruction.
 5. Apparatus according to claim 4 wherein said preliminary ejection means comprises a differentiation circuit coupled to said recording unit for generating a signal of predetermined duration for causing said preliminarily ejected ink droplets to be ejected for said first given period of time which is a function of the duration of the signal generated by said differentiation circuit.
 6. Apparatus according to claim 4 wherein said detection means includes means for resetting said timing means upon detection of each print command signal.
 7. Apparatus according to claim 4 wherein said control means includes a further delay means for disabling said preliminary ejection means a predetermined period of time after detection of said print command signal.
 8. Apparatus according to claim 4 wherein said control means includes memory means for memorizing when the interval between successive print command signals exceeds said predetermined period of time as measured by said timing means.
 9. Apparatus according to claim 8 wherein said delay means is coupled to said memory means for resetting said memory means after said predetermined period of time. 